I bought a KVM switch which is hooked to windows PC and a Linux Mint 13 KDE. The hot key scroll lock + scroll lock works fine on windows but not on Linux. One solution that I found was to key in Ctrl+Alt+F1 to switch to command line and then Scroll lock + Scroll lock to change to Windows PC. When back on Linux box key in CTRL+F7 to go back to GUI. This works fine however adds an extra step. Another solution is to add and entry to xmodmap However, when I execute the command I keep on getting the output below.

Trying to solve a completely different problem, I discovered there's a bug (at least one, but I suspect more) in udev that causes, among other things, that "no protocol specified" message. I make no claims to understand any of it

I don't know if you've seen that in your travels around the web, but if not, maybe try adding udev to your search terms. I wish you much better luck than I've had solving the problem.